[PATCH v3 04/15] KVM: Extend the memslot to support fd-based private memory

Chao Peng
2021-12-21T15:12:48Z

Extend the memslot definition to provide fd-based private memory support
by adding two new fields(fd/ofs). The memslot then can maintain memory
for both shared and private pages in a single memslot. Shared pages are
provided in the existing way by using userspace_addr(hva) field and
get_user_pages() while private pages are provided through the new
fields(fd/ofs). Since there is no 'hva' concept anymore for private
memory we cannot call get_user_pages() to get a pfn, instead we rely on
the newly introduced MEMFD_OPS callbacks to do the same job.

This new extension is indicated by a new flag KVM_MEM_PRIVATE.

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
include/linux/kvm_host.h | 9 +++++++++
include/uapi/linux/kvm.h | 12 ++++++++++++
2 files changed, 21 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 865a677baf52..96e46b288ecd 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -433,8 +433,17 @@ struct kvm_memory_slot {
u32 flags;
short id;
u16 as_id;
+ struct file *file;
+ u64 file_ofs;
};

+static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot)
+{
+ if (slot && (slot->flags & KVM_MEM_PRIVATE))
+ return true;
+ return false;
+}
+
static inline bool kvm_slot_dirty_track_enabled(struct kvm_memory_slot *slot)
{
return slot->flags & KVM_MEM_LOG_DIRTY_PAGES;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e3706e574bd2..a2c1fb8c9843 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -103,6 +103,17 @@ struct kvm_userspace_memory_region {
__u64 userspace_addr; /* start of the userspace allocated memory */
};

+struct kvm_userspace_memory_region_ext {
+ __u32 slot;
+ __u32 flags;
+ __u64 guest_phys_addr;
+ __u64 memory_size; /* bytes */
+ __u64 userspace_addr; /* hva */
+ __u64 ofs; /* offset into fd */
+ __u32 fd;
+ __u32 padding[5];
+};
+
/*
* The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace,
* other bits are reserved for kvm internal use which are defined in
@@ -110,6 +121,7 @@ struct kvm_userspace_memory_region {
*/
#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
#define KVM_MEM_READONLY (1UL << 1)
+#define KVM_MEM_PRIVATE (1UL << 2)

/* for KVM_IRQ_LINE */
struct kvm_irq_level {
--
2.17.1